Corn Fiber as a Biomass Feedstock for Production of Succinic Acid

The selection of an economical carbon source is a fundamental parameter to establish a successful industrial succinic acid (SA) bioprocess. In this work, corn fiber (CF), a renewable and an inexpensive source of carbohydrates, was successfully used for bioproduction of SA. Optimized liquid hot water (LHW) pretreatment followed by enzymatic hydrolysis were used to obtain corn fiber hydrolysate (CFH). Results in batch fermentation with Actinobacillus succinogenes showed that a control solution mimicking CFH produced 28.7 g/L of SA with a yield of 0.67 g SA/g sugars, while fermentation of CFH produced 27.8 g/L of SA with a yield of 0.61 g SA/g sugars. It was found that culture pH was a critical factor affecting SA production. In sodium acetate buffered media, SA was the major end-product with lower levels of acetic acid (AA) and formic acid (FA). When unbuffered media was used, lactic acid (LA) and ethanol were also detected

Increasing Cis-lycopene Content of the Oleoresin from Tomato Processing Byproducts Using Supercritical Carbon Dioxide and Assessment of Its Bioaccessibility

In recent years, health- and wellness-promoting foods have been one of the major focus of consumers; therefore, the food industry is increasing its efforts in developing these food products. Tomatoes, tomato-food products and their byproducts have gained special attention in virtue of the carotenoids-rich source that they represent, especially lycopene (~90%). The role of lycopene in human diet has been highlighted as a result of its direct relationship with the decrease of chronic diseases. Nevertheless, lycopene is water-insoluble making its extraction simple with organic-toxic solvents; in addition, lycopene degrades easily with light, time, and storage. Lycopene exist in nature mostly in trans-lycopene (~95%); however, cis-lycopene isomers provide potentially better health benefits than the trans-lycopene isomeric form due to their higher bioavailability. The main objective of this thesis was to increase the bioaccessibility of the lycopene in the tomato oleoresin by SC-CO2 extraction. Specific objectives were to extract oleoresin from tomato processing byproducts, namely, tomato seed and peel, using SC-CO2 and optimize the extraction conditions for the highest cis-lycopene content, and to test the bioaccessibility of the SC-CO2-extracted lycopene in vitro. The highest oleoresin yield (24.6%) was obtained from 100% seed blend with SC-CO2 extraction at temperature of 40 °C and pressure of 50 MPa, whereas the highest cis-lycopene content was achieved at temperature of 80 °C and pressure of 30 MPa from 100% peel. SC-CO2-extracted oleoresins contained 67% of cis-lycopene, while the hexane-extracted ones had 34%. When insoluble fraction was removed, the oil fraction contained up to 82% of cis-lycopene in SC-CO2 extracted oleoresins. SC-CO2 extraction increased the bioaccessibility of lycopene approximately 2-folds in the oleoresin and 2.4-folds in the oil fraction compared to hexane extraction (p2-extracted oleoresin. The bioaccessibility of the lycopene in the oil fraction was 1.7 and 4.0% for the hexane and SC-CO2-extracted oleoresins, respectively. Lycopene concentration in the digesta increased when the tomato oleoresin was used compared to oil fraction for both SC-CO2 and hexane extractions. After digestion of tomato peel oleoresin, lycopene concentration in the final digesta was 4.6 and 13.4 μg/g for hexane- and SC-CO2-extracted oleoresin, respectively. Oil fraction of the tomato peel oleoresin released concentrations of lycopene of 1.3 μg/g for hexane and 3.0 μg/g for SC-CO2 extracted oleoresin. SC-CO2 can enhance the efficacy of lycopene during extraction stage in a simple and clean way. The use of cis-lycopene-rich extract from tomato processing byproducts in traditional foods can improve the functional properties of the product while adding value to the byproducts of the tomato industry processing industry. Advisor: Ozan N. Ciftc